Primastar transmission issues

That sounds like a pain. A faulty transmission oil pressure sensor could definitely cause those symptoms. Have you checked the gearbox oil level? Low oil level can mess with the pressure and trigger the sensor, throwing everything into disarray. What kind of diagnostic tool did you use to pull the error code? Was it a generic OBD2 reader, or something more specific to Nissan?

I used a generic OBD2 reader. Where is the fill point to check the gearbox oil level on the Primastar? Is it easy to access? If the level is low, is it likely just a top-up job, or could there be a leak somewhere?

Yeah, a generic reader will give you the code, but not much else. Regarding the fill point, it's typically on the side of the transmission. You'll usually find a bolt or plug that you can remove. Access can be a bit tight depending on the van's configuration, so you might need some extensions for your tools. If it's low, topping it up might help temporarily, but you absolutely need to find the source of the loss. A slow leak around a seal could easily be the culprit. Given the emergency mode and shifting issues, honestly, I'd suggest having a workshop take a look. They can pressure test the system and pinpoint any leaks or internal damage much more effectively. I had one with similar symptoms after ignoring a slight leak for some time!

Thanks for the advice, I appreciate it. I booked it into a local workshop, and you were spot on. The gearbox oil level was low due to a slight leak. They replaced the sensor and the leaking seal, topped up the oil, and cleared the fault codes. Cost me 365€ all in. Shifts like new now.